WO2006091633A2 - Active vibration control actuator such as used in an engine mount - Google Patents

Abstract

Rubber bearings (60) are used in an active actuator since they allow the resonant frequency, or active actuator to be used as force multiplier at a specified frequency. The rubber bearings (60) permit large axial motion while constricting radial motion. In addition, incorporating an active actuator between the first (26) and second (28) chambers of an otherwise standard fluid filled engine mount allows the changes in the motion of the actuator to correspond to pressure changes in the mount itself. These changes can be forced or measured so that any signal could control the motion of the actuator and thus the dynamic pressure level in an engine mount or fluid mount.

Description

ACTIVE VIBRATION CONTROL ACTUATOR SUCH AS USED IN AN ENGINE MOUNT

Background of the Invention

[0001] This application claims priority from U.S. Provisional Application

60/655,692, filed February 23, 2005, the disclosure of which is incorporated herein by reference.

[0002] This application relates to an active vibration control actuator, such as used to actively damp vibrations. One area where such an active vibration control actuator is used is in an engine mount such as an active hydromount, although the invention should not be limited thereto.

[0003] Engine mounts are used to connect or support between two components of an automotive vehicle, for example an engine or vehicle motor and the chassis or frame. It is common to use an engine mount that has a first member secured to the engine and a second member that is secured to the frame. A wall extends between the first and second members and forms a chamber. For example, it is common to use an elastomer or rubber between the first and second members to damp the vibrations between these automotive vehicle components. It is further known to employ an electromagnetic actuator to damp and isolate vibrations. For example, U.S. Patent No. 4,624,435 illustrates such an arrangement. [0004] Moreover, it is also known to use such an arrangement in which a fluid chamber or hydromount is involved. For example, U.S. Patent Nos. 5,297,781; 4,802,648; 4,650,170; and 4,869,474 describe exemplary arrangements. [0005] For vibration control products, both resonant and isolation conditions must be taken into consideration. The frequency of response in one area (resonance) generates the need for high damped products that yield poor characteristics in the isolation frequency (audible) range. Consequently, a simple and easily controlled active vibration control actuator such as used in a hydromount is proposed.

[0006] A standard fluid-filled engine mount controls road excitations through a passive resonator mechanism that includes fluid flow through a channel, located between first and second chambers (a main chamber and a compensation chamber). Road induced vibrations are typically in the frequency range of 5-15 hertz, and can be handled simply by the passive means of using a volumetric fluid - -

amplifier to act on a fluid mass through a channel (essentially a Helmholtz-type resonator). Such an arrangement provides for frequency dependent damping, and can be tuned to the bounce frequency of the engine itself. However, a dynamic device is central to this mount and allows dynamic activation to control high frequency isolation. One control mechanism this part would have is passive and damps at low frequencies. This is generally known. The other control mechanism is to provide an active dynamic control in an effort to provide near zero force transmission in the audible or human hearing range frequency spectrum of 20-2Ok hertz.

[0007] Thus, there is a desire to employ an active actuator so that changes in the motion of the actuator correspond to pressure changes in the mount itself, and can be forced or measured. For example, the actuator can receive signals from an electrical signal that could vary with engine rpm. Active control, on the other hand, intends to reduce transmitted forces before they are transmitted. Thus, a need exists for a simple device that allows both passive and active frequency components in the mount itself and not in the controller, and also provides potential for a simple feed forward unit to control the device.

[0008] It is also known that such actuators provide the oscillating motion needed for damping purposes. In the past, numerous means allowed for large axial movement while controlling radial displacement via steel springs or fabric. The ability to use the resonant frequency of the device as a force multiplier at a specific frequency would also be desirable.

Summary of the Invention

[0009] An electrical actuator applies a reciprocating force that attenuates vibrations between the associated engine and the associated vehicle frame. The actuator includes a first portion and a second portion that selectively reciprocate relative to one another. An elastomer is connected to the first portion and connected to the second portion such that relative reciprocating motion is permitted and relative motion in another direction is constrained.

[0010] More particularly, an engine mount is provided that includes first and second members secured to one of an associated engine and associated vehicle frame, respectively. A wall is interposed between the first and second members and - O -

forms a chamber. An electrical actuator applies a reciprocating force that attenuates vibrations between the associated engine and the associated vehicle frame. The actuator includes a first portion and a second portion that selectively reciprocate relative to one another. An elastomer is connected to the first portion and connected to the second portion such that relative reciprocating motion is permitted and relative motion in another direction is constrained.

[0011] The engine mount chamber may also include a hydraulic fluid, and a passage having a limited cross-sectional area that damps vibrations based on the resonant fluid flowing through the passage.

[0012] The elastomer constrains relative movement of the first and second portions at an angle generally perpendicular to the direction of permissive relative reciprocating motion.

[0013] In another embodiment of the engine mount, a piston is secured to one of the first portion and second portion of the actuator. An additional elastomer is connected to the piston and connected to the wall to permit selective reciprocating motion of the piston relative to the wall, and constrain movement of the piston in another direction.

[0014] The elastomer acts as a force multiplier at a specific frequency thereby generating higher forces at a selected frequency.

[0015] An improved hydromount includes first and second fluid chambers separated by a wall and communicating with one another through a passage in the wall. An active actuator is received in one of the first and second fluid chambers and receives signals from an associated processor to control motion of the actuator.

[0016] The actuator forms a portion of the wall and in one preferred arrangement separates the first and second fluid chambers. The actuator includes first and second portions that selectively move relative to one another in response to signals from the associated processor so that a pressure level in the other of the first and second chambers is dynamically controlled.

[0017] The present concepts are applicable to active vibration control actuators, and may find particular application in engine mounts such as active hydromounts.

[0018] Another advantage of the invention is that the rubber bearings allow use of the resonant frequency of the device as a force multiplier at a specific - -

frequency. This makes the device capable of generating higher forces at a selected frequency which is an advantage over prior art arrangements.

[0019] Still another feature is to use softer or stiffer rubber in order to control the frequency, as well as more or less mass on the magnet.

[0020] The incorporation of the actuator itself, i.e., volumetric actuator inside a fluid filled engine mount, and means for separating and dealing with passive and active frequency components in the mount itself and not the controller, as well as the possibility of a simple feed forward unit to control the device are still other beneficial features of the invention.

[0021] Still other features and benefits will become apparent to one skilled in the art upon reading and understanding the following detailed description.

Brief Description of the Drawings

[0022] FIGURE 1 is a cross-sectional view through an engine mount, particularly, an active hydromount with schematic representation of providing a signal to the actuator.

[0023] FIGURE 2 is an enlarged cross-sectional view of an actuator incorporating the rubber bearings.

[0024] FIGURE 3 is a cross-sectional view of the rubber bearings incorporated into an active hydromount.

Detailed Description of the Preferred Embodiment

[0025] Turning first to FIGURE 1 , a first member 10 includes a threaded recess 12 for securing the first member to one of an engine 14 or frame or chassis 16. In this instance, the first member 10 is secured to the engine via a stud in a manner generally well known in the art. A second member 18 of the engine mount is shown as a housing structure that may be partially encapsulated in rubber or formed in portions that are secured together. A wall 20 of an elastomer or rubber material connects the first and second members 10, 18. The elastomer provides a resistance to axial compression and acts as a support between the first and second members while advantageously providing a self-damping effect as a result of its elstic nature and high deflection to load ratio. In addition, a separating wall 22 includes a passage 24 that allows a first or lower chamber 26 to be in fluid communication with - -

a second or upper chamber 28. As is known, oscillations of different frequency and amplitudes when applied between the first and second members displace a fluid, such as a hydraulic fluid, between the first and second chambers 26, 28. Because the passage 24 has a predetermined cross-sectional area, the vibrations are damped as a result of this transmission between the first and second members. Such a structure is generally known as shown and described in U.S. Patent No. 5,297,781 , for example. The engine mount or hydromount, as it is referred to with the hydraulic fluid, further includes wall 40 to define the second chamber 28. Thus, the first chamber 26 is defined in part by the inner surface of elastomeric wall 20 and the rigid wall 22 that separates the first chamber from the second chamber 28. The second chamber, on the other hand, is at least partially defined by the separating wall 22 and wall 40.

[0026] Likewise, actuators that exert active attenuation are also generally known in the art. Typically, they include a piston that extends into the fluid chamber. Thus, the particular details of the structure and operation of an actuator are generally known and need not be repeated here as it will be understood by one of ordinary skill in the art. However,, this arrangement incorporates the actuator A into the wall 22 so that a first face 42 forms a portion of the surface defining the first chamber 26. Likewise, the second face 44 forms a portion of the wall defining the second chamber 28. A signal provided by a digital signal processor, that is amplified and provided through line 46 to the actuator, results in selective oscillation of the actuator, namely, central portion 50. The coil and electromagnet assembly 52 result in selective reciprocation in an axial direction represented by axis Y. Employing an active actuator between the main fluid chamber and the compensation chamber changes the motion of the actuator to correspond to pressure changes in the mount itself, and can be forced or measured. That is; the actuator receives signals from an electrical signal processor/generator that can vary with engine rpm, for example. The process signal can have both frequency and phase content. Any signal can control the motion of the actuator and thus the dynamic pressure level in the fluid mount, namely in the first and second chambers 26, 28. As will be appreciated, the actuator is fixed to wall 22.

[0027] Because the dynamic stiffness of both elastomeric and hydraulic engine mounts is a function equal to the peak-to-peak transmitted force divided by - o -

the peak-to-peak displacement, it is possible to reduce the dynamic stiffness to near zero by reducing the transmission forces to near zero. Actively reducing transmitted forces, i.e., before they are transmitted is the operating principle of active control philosophy. Because of the simplicity of the engine mount devices as shown in FIGURE 1 , this can all easily be achieved. The active hydromount controls road excitations through a passive resonator mechanism consisting of fluid flow through passage 24 interposed between the first and second chambers 26, 28. Road induced vibrations will typically be in the frequency of 5-15Hz, and can be handled simply by the passive means of using this volumetric fluid amplifier to act on a fluid mass through passage 24. This provided for frequency dependent damping and can be tuned to the bounce frequency of the engine itself, as has been done in a commercially successful manner in the past.

[0028] However, incorporating a dynamic device such as described with reference to FIGURE 1 , allows dynamic activation to control high frequency isolation. Thus, one control mechanism this part would have is passive, as described above, while the other control mechanism, i.e., the active actuator, provides for active dynamic control for near zero force transmission in the audible or human hearing range frequency spectrum of 20-22 kilohertz.

[0029] In summary, this invention also provides an actuator that is a volumetric actuator inside a fluid filled engine mount, means to separate and deal with passive and active frequency components in the mount itself as opposed to dealing with it via the controller, and also providing a simple feed forward unit to control the engine mount device.

[0030] FIGURES 2 and 3 more particularly illustrate the actuator itself

(FIGURE 2) and the incorporation of the actuator in a hydromount assembly (FIGURE 3). As noted above with respect to FIGURE 1 , the actuator provides oscillating motion in the engine mount or hydromount. In the past, numerous means allow for the large axial movement while controlling radial displacement via steel springs or fabric. It is proposed in accordance with the present invention that rubber be used to allow large axial movement while constraining radial motion, i.e., motion generally perpendicular to axis Y or at least in a direction different than that along the axis Y. Here for example, as shown in FIGURE 2, rubber bearings 60 are provided in the actuator A'. The first portion 62 of the actuator is adapted to oscillate or move relative to second portion 64 in response to signals provided by a controller or processor (not shown in FIGURE 2) provided to an electromagnet or coil. Thus, as is conventionally known, displacement of the actuator can be controlled through signal processing and likewise impact on damping vibration as desired. Including the rubber bearings still permits a large axial motion, but also advantageously restricts the radial motion. The rubber bearings can be used in both active vibration control actuators as generally represented by FIGURE 2, as well as in active engine mounts or hydromounts of the type shown in FIGURE 1 or in FIGURE 3. The rubber bearings are important Because they permit the use of a resonant frequency of the device as a force multiplier at a specific frequency. Stated another way, this allows the actuator or engine mount/hydromount to generate higher forces at a selected frequency which is an advantage not found in the prior art. Moreover, that frequency can be controlled by using softer or stiffer rubber, for example. Still another way to control the frequency is to add greater mass to the magnet or reduce the mass of the magnet. However, the incorporation of rubber bearings into either an active vibration control actuator or active hydromount provides for rubber springs in such devices that have heretofore been unknown.

[0031] As shown in FIGURE 3, the actuator A" is slightly modified by incorporating a rubber bearing 70 that is secured to a first or moveable actuator portion 72 (for example along a radial inner portion thereof) and is also secured to second member 18". Thus, the nature of rubber is to allow the oscillation in a direction generally along the Y axis but constraining the movement in the radial direction or perpendicular to the Y axis.

[0032] Moreover, this arrangement illustrates use of a piston 74 extending from the actuator and mounted at one end of rod 76 secured to the first actuator portion 72. As the piston oscillates, a second rubber bearing encapsulating piston 74 serves as a divider between the first or lower chamber 26" and the second or upper chamber 28" that is otherwise separated by wall 22" having passage 24" extending therethrough. Again, this additional elastomer or second rubber bearing that encapsulates the piston and is secured to wall 22" permits axial oscillation of a relatively large magnitude while constraining movement in the radial direction. [0033] The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon - o -

reading and understanding the preceding detailed description. For example, other types of engine mounts, hydromounts, or use of the active actuator assemblies in other environments could be used incorporating one or more of these features. The rubber bearing feature shown in FIGURES 2 and 3 could likewise be incorporated into the structure shown in FIGURE 1 of a feed forward active hydromount. Likewise, different materials of construction can be used without departing from the scope and intent of the present invention. It is intended that the invention instead be construed as including all such modifications and alterations insofar as they fall within the scope of the appended claims.

Claims

- -Having thus described the invention, it is now claimed:

1. An engine mount comprising: a first member adapted to be secured to one of an associated engine and associated vehicle frame; a second member adapted to be secured to the other of the associated engine and associated vehicle frame; a wall interposed between the first and second members and forming a chamber; and an electrical actuator for applying a reciprocating force that attenuates vibrations transmitted between the associated engine and associated vehicle frame, the actuator including a coil portion and a magnet portion that are adapted to selectively reciprocate relative to one another, an elastomer connected to the coil portion and connected to the magnet portion such that relative reciprocating motion is permitted and relative motion in another direction is constrained.

2. The invention of claim 1 wherein the elastomer is rubber.

3. The invention of claim 1 wherein the chamber includes a hydraulic fluid.

4. The invention of claim 3 wherein the wall includes a passage therethrough having a limited cross-sectional area that damps vibrations based on the resonance of fluid flowing through the passage.

5. The invention of claim 1 wherein the elastomer constrains relative movement of the coil portion and magnet portion at an angle generally perpendicular to the direction of permissive relative reciprocating motion.

6. The invention of claim 1 further comprising a piston secured to one of the coil portion and magnet portion, and an additional elastomer connected to the piston and connected to the wall.

7. The invention of claim 6 wherein the additional elastomer permits selective reciprocating motion of the piston relative to the wall, and constrains movement of the piston in another direction.

8. The invention of claim 7 wherein the elastomer and additional elastomer act as a force multiplier at a specific frequency thereby generating higher forces at a selected frequency.

9. A hydromount comprising: a first fluid chamber; a second fluid chamber; a wall separating the first and second fluid chambers; a passage through the wall providing operative fluid communication between the first and second fluid chambers; and an active actuator received in one of the first and second fluid chambers, the actuator adapted to receive signals from an associated processor to control motion of the actuator.

10. The invention of claim 9 wherein the actuator forms a portion of the wall separating the first and second fluid chambers, the potion being selectively movable relative to the wall in response to selected signals from the associated processor.

11. The invention of claim 10 wherein the actuator includes first and second portions that selectively move relative to one another in response to selected signals from the associated processor, the actuator first portion fixed to a nop- moving part of said one of the first and second fluid chambers, and the actuator second portion defining the wall portion such that a pressure level in the other of the first and second chambers is dynamically controlled.

12. An electrical actuator for applying a reciprocating force that attenuates vibrations transmitted between relatively moveable first and second components, the actuator includes a first portion and a second portion that are adapted to selectively reciprocate relative to one another, an elastomer is connected to the first portion and connected to the second portion such that relative reciprocating motion in one direction is permitted and relative motion in another direction is constrained